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BAI 511

Advanced Routing ProtocolsEIGRP Part 1

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EIGRP Part 1

Review

Wildcard masks

Authentication

Passive Interfaces

Stuck-in-active

Stub Routers

Variance

Ip-bandwidth percent

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Review

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What do we remember about EIGRP?

What type of protocol is EIGRP?

Distance Vector

What are the default metrics used by EIGRP?

Bandwidth (slowest) and Delay (cumulative) What are the optional metrics?

Reliability and Load

What algorithm is used to determine best path?

DUAL (Diffusing Update Algorithm)

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Review of EIGRP from CCNA

Enhanced Interior Gateway Routing Protocol (EIGRP)

Released in 1992 with Cisco IOS Software Release 9.21.

Enhancement of Ciscos:

Interior Gateway Routing Protocol (IGRP).

Both are Cisco proprietary, operate only on:

Cisco routers

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RTP and EIGRP

Packet Types

What transport layer protocol does EIGRP use?

Reliable Transport Protocol (RTP)

Why doesnt EIGRP use UDP or TCP?

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Protocol-

Dependent

Modules

EIGRP uses protocol-dependent modules (PDM). to route

different protocols, including:

IP

Internetwork Packet Exchange (IPX)

AppleTalk,

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EIGRP Packet

TypesHello

Packet

What are Hello packets used for by EIGRP to:

Discover neighbors (sometimes called neighborsh ips )

Form adjacencies with those neighbors What is the multicast address? Hint: 224.0.0.?

224.0.0.10

Are these sent as reliable or unreliable deliver?

Unreliable delivery No ACKs returned

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Hello Protocol

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Hello Protocol

Default hold time - 3 times the hello interval

If the hold timeexpires:

EIGRP declares the route as down

DUAL searches for a new path in the topology table or by

sending out queries.

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Update Packets Reliable Delivery

Acknowledgment (ACK) Packets

Sent when reliable delivery is used (update, query, and reply

packets).

EIGRP uses

triggered

updates

EIGRP Packet Types

Update and

AcknowledgementPackets

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EIGRP Packet

TypesQuery

and ReplyPackets

Queries and replies use reliable delivery.

Used by DUAL when searching for networks and other tasks.

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DUAL: An Introduction

J. J. Garcia-Luna-Aceves

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DUAL: An Introduction

.

XOr holdtime expires

R2: Checks

Topology table forFeasible

Successor. If no

FS

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Summary - RTP Packet Types

Hellos Identifies neighbors

Used by the neighbor discovery and recovery process.

Multicast

Unreliable delivery

Acknowledgements (ACK) Acknowledges receipt

Hello packets with no data

Unicast

Unreliable delivery Updates Advertises routes

Transmitted only when necessary

Unicast when sent to a specific router

Multicast when sent to multiple routers

Reliable delivery

Queries Ask about a route (DUAL) Reliable delivery

Multicast or Unicast

Queries and Replies Ask about a route and answer a query (DUAL)

Reliable delivery

Replies: Unicast

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Administrative Distance

When compared to other

interior gateway protocols(IGP), EIGRP is the most

preferred by the Cisco IOS

software because it has the

lowest AD.

Laterin this chapter, you

learn how to configure EIGRP

summary routes.

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Configuring Hello Intervals and Hold Times

Configurable on a per-interface basis, NOT per neighbor (LANs)

Does not have to match with other EIGRP routers to establish

adjacencies.

Router(config-if)# ip hello-intervaleigrpas-number seconds

Router(config-if)# ip hold-time eigrp as-number seconds

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The show ip eigrp interfaces detail command displays a router's

EIGRP Hello timer setting for each enabled interface.

R3# show ip eigrp neighbors detail

IP-EIGRP neighbors for process 1

H Address Interface Hold Uptime SRTT RTO Q Seq Type

(sec) (ms) Cnt Num

3 10.0.0.18 Se0/3 13 01:03:55 24 200 0 5

Version 12.3/1.2, Retrans: 2, Retries: 0

2 10.0.0.14 Se0/2 14 01:04:08 29 200 0 4Version 12.3/1.2, Retrans: 1, Retries: 0

1 10.0.0.5 Se0/0 13 01:09:52 607 3642 0 13


0 10.0.0.9 Se0/1 12 01:10:19 60 360 0 21


R3#

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Router-ID

EIGRP Router ID is an IP address used to uniquely identify an

EIGRP router.

1. Use the IP address configured with the EIGRP router-id

command.

2. Highest IP address of any of itsloopback interfaces.

3. Highest act iveIP address of any of its physical interfaces.

Router(config)# routereigrpas

Router(config-router)# router-idip-address

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Forming Neighbor Adjacencies

Per interface/subinterface not per neighbor

The following are the most common causes of problems with EIGRPneighbor relationships:

Unidirectional link

Uncommon subnet, primary, and secondary address mismatch

Mismatched masks

K value mismatches

Mismatched AS numbers

Stuck in active

Layer 2 problem

Access list denying multicast packets Manual change (summary router, metric change, route filter)

Does NOT prevent neighbor relationships

Hello and Hold timer setting mismatch

Duplicate router IDs

IP MTU mismatch

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The Metric

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Metric

By default, K1 and K3 are set to 1, and K2, K4, and K5 are set to 0.

The result is that only the bandwidth and delay values are used inthe computation of the default composite metric.

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Metric

The K values on R1 are set to the default.

Changing these values to other than the default is not recommended

unless the network administrator has a very good reason to do so.

Cisco recommends that these values are not modified.

R1# show ip protocols

Routing Protocol is eigrp 1

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Default networks flagged in outgoing updates

Default networks accepted from incoming updates

EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0

K1 K2 K3 K4 K5

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Metric: Displaying Interface Values

Westasman> show interface fa0/0

Ethernet0 is up, line protocol is up

Hardware is Lance, address is 0010.7b3a.cf84 (bia 0010.7b3a.cf84)

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

rely 255/255, load 1/255

SanJose2> show interface s0/0

Serial0/0 is up, line protocol is up

Hardware is QUICC Serial

Description: Out to Westasman

Internet address is 192.168.64.5/30

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

rely 255/255, load 246/255

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DUAL Concepts

Diffusing Update Algorithm is the algorithm used by

EIGRP.

Determines:

best loop-free path

loop-free backup paths (which can be used immediately)

DUAL also provides the following:

Fast convergence

Minimum bandwidth usage with bounded updates

DUAL uses several terms that are discussed in more detail

throughout this section:

Successor Feasible distance

Feasible successor

Reported distance or advertised distance

Feasible condition or feasibility condition

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Feasible distance (FD) is the minimum distance (metric) along a path to a

destination network.Reported distance (RD) is the distance (metric) towards a destination as advertised

by an upstream neighbor. Reported distance is the distance reported in the

queries, the replies and the updates.

A neighbor meets the feasible condition (FC) if the reported distance by the

neighbor is less than the current feasible distance (FD) of this router. "If a

neighbors metric is less than mine, then I know the neighbor doesn't have a loop

going through me."

A feasible successoris a neighbor whose reported distance (RD) is less than the

current feasible distance (FD). Feasible successor is one who meets the feasible

condition (FC).

Your route (metric) to the network (RD to me) must be LESS than my current route

(my total metric) to that same network. If your route (metric) to the network (RD to

me) is LESS than my current route (my total metric), I will include you as a

FEASIBLE SUCCESSOR.

If your route (metric) to the network (RD to me) is MORE than my current route (my

total metric), I will NOT include you as a FEASIBLE SUCCESSOR.

Successors and Feasible Successors

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Example 1: Best Path (Successor)? Feasible Successor?

R1

R2

R3

S0/0

S0/1

RD = 6,000,000

RD = 3,000,000

FD = 6,500,000

FD = 3,500,000

Network X

FD = RD + additional Delay of serial link between R1 and neighbor.

(This could also be due the slowest bandwidth.)

Which router isthe successor?

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Example 1

R1

R2

R3

S0/0

S0/1

RD = 6,000,000

RD = 3,000,000

FD = 6,500,000

FD = 3,500,000

Network X

FD of3,500,000 is the metric for network X in the routing table for

R1.

Successor

Is R2 a feasiblesuccessor?

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Example 1

R1

R2

R3

S0/0

S0/1

RD = 6,000,000

RD = 3,000,000

FD = 6,500,000

FD = 3,500,000

Network X

RD of R2 is greater than FD through R3.

Does not meet FC.

No FS.

Successor

NOT a Feasible

Successor

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Example 1

R1

R2

R3

S0/0

S0/1

RD = 6,000,000

RD = 3,000,000

Network X

Maybe R2s path to Network X includes R1 - Loop

Successor

NOT a FeasibleSuccessor

RX

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Example 1

R1

R2

R3

S0/0

S0/1

RD = 6,000,000

RD = 3,000,000

Network X

Or maybe R2s does have a valid path to Network X.

But R1 cant tell because the distance vector update only gives it

distance and direction.

Successor

NOT a FeasibleSuccessor

RX

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Example 2: Best Path (Successor)? Feasible Successor?

R1

R2

R3

S0/0

S0/1

RD = 4,000,000

RD = 3,000,000

FD = 5,500,000

FD = 4,500,000

Network X

FD = RD + additional Delay of serial link between R1 and neighbor.

(This could also be due the slowest bandwidth.)

Successor

FeasibleSuccessor?

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Example 2

R1

R2

R3

S0/0

S0/1

RD = 4,000,000

RD = 3,000,000

FD = 5,500,000

FD = 4,500,000

Network X

RD of R2 is less than (or equal to) the FD through R3.

Meets FC, there is no loop back through R1.

Is a FS.

Successor

FeasibleSuccessor

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X

Queries

Replies

RtrF

RtrC

RtrE

RtrD

RtrB

RtrA

RtrG

If there are no Feasible Successors, the router must ask neighbors for help in hope offinding a new, loop-free path to the destination.

Neighbor routers are compelled to reply to this query.

If a neighbor has a route, it will reply with information about the successor(s).

If not, the neighbor notifies the sender that it doesnt have a route to the destinationeither.

Looking for new route

Query and Reply Packets

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Configuring EIGRP

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Our Topology

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Preconfigs

Configured on all routers.

R1(config)# no ip domain lookup

R1(config)# line con 0

R1(config-line)# exec-timeout 0 0

R1(config-line)# logging synchronous

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R1

Bandwidth of 1,424 Kbps (1,424,000 bps) between R3 and R4 on

bottom link

1544 configured on all serial links just in case.

interface FastEthernet0/0

ip address 192.168.10.1 255.255.255.0

!

interface Serial0/0

bandwidth 1544

ip address 10.0.0.1 255.255.255.252

clock rate 64000

!

interface Serial0/1

bandwidth 1544

ip address 10.0.0.5 255.255.255.252

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R2


ip address 192.168.20.1 255.255.255.0

!

interface Serial0/0

bandwidth 1544

ip address 10.0.0.2 255.255.255.252

!

interface Serial0/1

bandwidth 1544ip address 10.0.0.9 255.255.255.252

clock rate 64000

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R3


ip address 192.168.30.1 255.255.255.0

!

interface Serial0/0

bandwidth 1544

ip address 10.0.0.6 255.255.255.252

clockrate 64000

!

interface Serial0/1

bandwidth 1544

ip address 10.0.0.10 255.255.255.252

!

interface Serial0/2

bandwidth 1544ip address 10.0.0.13 255.255.255.252

clockrate 64000

!

interface Serial0/3

bandwidth 1424

ip address 10.0.0.17 255.255.255.252

clockrate 64000

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R4


ip address 172.16.1.1 255.255.255.0

!

interface Serial0/0

bandwidth 1544

ip address 10.0.0.14 255.255.255.252

!


ip address 172.16.2.1 255.255.255.0!

interface Serial0/1

bandwidth 1424

ip address 10.0.0.18 255.255.255.252

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Configuring

EIGRP R1

Wildcard masks Specifically tells EIGRP which interfaces to be

enabled on.

If subnet mask is used IOS may convert it for the running-config.

Lets do R2, R3 and R4 serial interfaces with wildcard masks

R1(config)# router eigrp 1

R1(config-router)# network 10.0.0.0 0.0.0.3


R1(config-router)# network 192.168.10.0

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Configuring

EIGRP





R3(config)# router eigrp 1R3(config-router)# network 10.0.0.4 0.0.0.3









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Outputs

R3# show ip route

C 192.168.30.0/24 is directly connected, FastEthernet0/0

D 192.168.10.0/24 [90/2172416] via 10.0.0.5, 00:02:47, Serial0/0

D 172.16.0.0/16 [90/2172416] via 10.0.0.14, 00:02:39, Serial0/2D 192.168.20.0/24 [90/2172416] via 10.0.0.9, 00:17:22, Serial0/1

10.0.0.0/30 is subnetted, 5 subnets

C 10.0.0.8 is directly connected, Serial0/1


D 10.0.0.0 [90/2681856] via 10.0.0.5, 00:02:57, Serial0/0

[90/2681856] via 10.0.0.9, 00:02:57, Serial0/1



Why does R3 prefer the top link to 172.16.0.0?

It is 1,544 kbps link compared to 1,424 kbps link below

What do you notice aobut the 10.0.0.0 network? How many paths? R3 has equal cost paths to 10.0.0.0/30

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Outputs

Does R3 see R4 as a neighbor on both links?

Yes

R3# show ip eigrp neighbors


H Address Interface Hold Uptime SRTT RTO Q Seq

Type

(sec) (ms) Cnt Num

3 10.0.0.18 Se0/3 13 00:17:37 24 200 0 5

2 10.0.0.14 Se0/2 14 00:17:50 29 200 0 4

1 10.0.0.5 Se0/0 14 00:23:35 607 3642 0 13

0 10.0.0.9 Se0/1 12 00:24:01 60 360 0 21

R3#

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Outputs

Some other commands

R3# show ip eigrp neighbors detail


H Address Interface Hold Uptime SRTT RTO Q Seq Type

(sec) (ms) Cnt Num

3 10.0.0.18 Se0/3 13 01:03:55 24 200 0 5


2 10.0.0.14 Se0/2 14 01:04:08 29 200 0 4


1 10.0.0.5 Se0/0 13 01:09:52 607 3642 0 13


0 10.0.0.9 Se0/1 12 01:10:19 60 360 0 21


R3#

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Outputs

R3# show ip eigrp interfaces

IP-EIGRP interfaces for process 1

Xmit Queue Mean Pacing Time Multicast Pending

Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes

Se0/1 1 0/0 60 0/15 299 0

Se0/0 1 0/0 607 0/15 3031 0

Se0/2 1 0/0 29 0/15 143 0

Se0/3 1 0/0 24 0/17 50 0

R3#

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Routing Protocol is "eigrp 1"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Default networks flagged in outgoing updatesDefault networks accepted from incoming updates

EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0

EIGRP maximum hopcount 100

EIGRP maximum metric variance 1

Redistributing: eigrp 1

Automatic network summarization is in effect

Maximum path: 4

Routing for Networks:

10.0.0.4/30

10.0.0.8/30

10.0.0.12/30

10.0.0.16/30

192.168.3.0

Routing Information Sources:

Gateway Distance Last Update

10.0.0.9 90 00:03:03

10.0.0.14 90 00:03:03

10.0.0.5 90 00:03:11

10.0.0.18 90 00:03:03Distance: internal 90 external 170

What are these telling us?

K values

Variance, later

Directly connected networks

Neighbors

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Outputs

R3# show ip eigrp topology

P 10.0.0.0/30, 2 successors, FD is 2681856via 10.0.0.9 (2681856/2169856), Serial0/1

via 10.0.0.5 (2681856/2169856), Serial0/0

P 172.16.0.0/16, 1 successors, FD is 2172416

via 10.0.0.14 (2172416/28160), Serial0/2

via 10.0.0.18 (2312192/28160), Serial0/3successor

feasible successor

Feasible distance

Feasible distance: if this router was the successor.

Reported Distance

is less than

Feasible distance

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Outputs

Why does R3 show a third entry for 10.0.0.0/30? Why is R4 a non-feasible successor?

Reported distance > Feasible distance

There is a loop!!!

R3# show ip eigrp topology all-links

P 10.0.0.0/30, 2 successors, FD is 2681856, serno 13

via 10.0.0.9 (2681856/2169856), Serial0/1

via 10.0.0.5 (2681856/2169856), Serial0/0

via 10.0.0.18 (3845632/3193856), Serial0/3

successorsuccessor

non-feasible

successor

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Authentication

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Authentication

EIGRP authentication helps prevent Denial of Service (DoS) attacks.

Prevents attackers from forming neighbor relationships withlegitimate routers, preventing the advertisement of incorrect

routing information.

Does not provide any privacy.

No encryption.

EIGRP uses generic router key chains as storage locations for keys.

These classify keys into groups and enable keys.

Use the key chain name command in global configuration mode to

create a chain of keys with the label EIGRP-KEYS.

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R1(config)# key chain carkeys

R1(config-keychain)# key 1

R1(config-keychain-key)# key-string ford

R1(config)# interface Serial0/0

R1(config-if)# ip authentication mode eigrp 1 md5

R1(config-if)# ip authentication key-chain eigrp 1 carkeys



R1(config-if)# ip authentication key-chain eigrp 1 carkeys

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Authentication

R1# show key chain

Key-chain carkeys:

key 1 -- text "ford"

accept lifetime (always valid) - (always valid) [valid now]

send lifetime (always valid) - (always valid) [valid now]

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R2(config)# key chainmykeys





R2(config-if)# ip authentication key-chain eigrp 1mykeys

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R3(config)# key chain thekeys


R3(config-keychain-key)# key-string toyota



R3(config-if)# ip authentication key-chain eigrp 1 thekeys

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Authentication

Whats the problem?

R1# show ip eigrp nei



(sec) (ms) Cnt Num

0 10.0.0.2 Se0/0 13 00:18:12 40 240 0 49

R1#

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Authentication

invalid authentication = mismatch

missing authentication = message did not include an md5 digest

R1# debug eigrp packet

EIGRP Packets debugging is on

(UPDATE, REQUEST, QUERY, REPLY, HELLO, IPXSAP, PROBE, ACK, STUB,

SIAQUERY, SIAREPLY)R1#

*Mar 1 02:37:25.651: EIGRP: pkt key id = 1, authentication mismatch

*Mar 1 02:37:25.651: EIGRP: Serial0/1: ignored packet from 10.0.0.6,

opcode = 5 (invalid authentication)

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R3(config)# key chain thekeys





R3(config-if)# ip authentication key-chain eigrp 1 thekeys

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Authentication

Did we fix it?

R1# show ip eigrp nei



(sec) (ms) Cnt Num

1 10.0.0.6 Se0/1 13 00:04:11 36 216 0 79

0 10.0.0.2 Se0/0 13 00:18:12 40 240 0 49

R1#

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Multiple Keys

Multiple keys in a key chain, and the existence of valid lifetimes for

each key, can cause some confusion in regards to when the key are

used. The rules can be summarized as follows:

Sending EIGRP messages: Use the lowest key numberamong

all currently-valid keys

Receiving EIGRP message: Check the MD5 digest usingALL

currently-valid keys

key chain trees

key 1

key-string chestnut

accept-lifetime 13:30:00 Sep 25 2009 14:30:00 Oct 25 2009

send-lifetime 13:30:00 Sep 25 2009 14:30:00 Oct 25 2009

key 2

key-string birch

accept-lifetime 14:30:00 Oct 25 2009 infinite

send-lifetime 14:30:00 Oct 25 2009 infinite

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The key chain name and key numberused on the two routers do

not have to match.

The key string on each of the two potential neighbors must match

Check which keys are currently valid using the show key chain

command.

Both must be configured: ip authentication mode eigrp asn md5

ip authentication key-chain eigrp asn name-of-chain

Multiple Keys: Examine the configuration and the current time

(show clock) on both routers.

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Passive Interfaces

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Passive Interfaces

Two ways to prevent EIGRP from speaking sending EIGRP

messages on an interface.

1. Enable EIGRP on the interface using the EIGRP network command

Do NOT send any EIGRP messages on the interface by using

the passive-interface command. No Hellos, thus no neighbor adjacency

Prefix (interface subnet) is still advertised on other interfaces

2. Do NOT enable EIGRP on the interface,

Advertise about the connected route using route redistribution

using the redistribute connected configuration command.

More complicated

Less popular

Passive

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Passive

Interfaces

R1# show ip eigrp inter




Se0/0 1 0/0 34 0/15 163 0

Se0/1 1 0/0 31 0/15 147 0

Fa0/0 0 0/0 0 0/10 0 0

The show ip eigrp interfaces command displays working interfaces

on which EIGRP has been enabled, but omits passive interfaces.

A failure of the interface, or making the interface passive, would omit

the interface from the output of this command.

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No longer a neighbor.

Must include network command.


R1(config-router)#passive-interface fa 0/0

R1# show ip eigrp inter




Se0/0 1 0/0 32 0/15 151 0

Se0/1 1 0/0 28 0/15 139 0

R1#



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Verifying



10.0.0.0/3010.0.0.4/30

192.168.10.0

Passive Interface(s):

FastEthernet0/0

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R4(config-router)#passive-interface default

R4(config-router)# no passive-interface ser 0/0

R4(config-router)# no passive-interface ser 0/1



10.0.0.12/3010.0.0.16/30

172.16.0.0

Passive Interface(s):

FastEthernet0/0

FastEthernet0/1

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Stuck-In-Active

Router

C R D

St k i A ti (SIA)

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X

Replies

Router

A

Router

B

C Router D

Queries

X

X

When EIGRP returns a stuck in active (SIA) message, it means that it has

not received a reply to a query.

Summarization can help prevent SIA.

Stuck in Active (SIA)

SIA

St k i A ti (SIA)

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Typically, SIAs results when a router cannot answer a query

because:

The router is too busy to answer the query

High CPU utilization

The router cannot allocate the memory to process the query Bad circuit between the routers (packet loss)

Unidirectional links

A link on which traffic can only flow in one direction due to a

failure

Solutions:

Stub Routers

Summarization

Stuck in Active (SIA)

T bl h ti (SIA) FYI

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Troubleshooting Steps:

Step 1: find the routes which are consistently being reported as stuck in active. If you are logging console messages, a quick perusal of the log will indicate

which routes are being marked as stuck in active most often.

Step 2: find out which routers are consistently failing to answer queries (not alwayseasy).

Use the show ip eigrp topologyactive command.

Any neighbors which have the rbeside them are neighbors that the

router is waiting on replies from the active timer is how long the route has been active.

pay particular attention to routes that have replies outstanding and havebeen active for 2 to 3 minute

Step 3: find the reason why that router is not receiving or answering queries

One you have found the router that is consistently not answering queries,

look for problems on the link to this neighbor, memory or CPU utilizationproblems with this neighbor, etc.

Troubleshooting (SIA) - FYI

T bl h ti (SIA) FYI

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SanJose2#show ip eigrp top all-linksCodes: P - Passive, A - Active, U - Update, Q - Query, R -

Reply, r - Reply status

A 10.2.4.0/24, 0 successors, FD is 512640000, Q1 replies, active 00:00:01, query-origin: Local origin

via 10.1.2.2 (Infinity/Infinity), Serial11 replies, active 00:00:01, query-origin: Local origin

via 10.1.3.2 (Infinity/Infinity), r, Serial3

Remaining replies:via 10.1.1.2, r, Serial0

Any neighbors that show an R have yet to reply (the active timer shows how long theroute has been active).

Pay particular attention to routes that have outstanding replies and have been active for

some time, generally two to three minutes.

Troubleshooting (SIA) - FYI

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Stub Routers

St b R t

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Stub Routers

Introduced with IOS 12.0

Stub router

Only has one neighbor

Only needs a default route

Commonly used in a hub and spoke network topology.

Helps with convergence Helps prevent SIA

Only the remote router is configured as a stub.

Only specified routes are propagated from the remote (stub) router.

Any neighbor will not query the stub router for any routes.

Stub router will send a special peer information packet to all neighboring routers toreport its status as a stub router.

X

Queries

Im a Stub

St b R t

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Stub Routers

This router is allowed to

Connected -Advertise connected routes, but only for interfaces

matched with a network command

Summary -Advertise auto-summarized or statically configured

summary routes

Static -Advertises static routes, assuming the redistribute

static command is configured

Redistr ibuted -Advertises redistributed routes, assuming

redistribution is configured

Receive-only - Does not advertise any routes. This option

cannot be used with any other option..


R3(config-router)# eigrp stuboption

St b R t

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Stub Routers

This is not the ideal place, but we will configure the stub network

here just to show the results.


R3(config-router)# eigrp stub connected

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Stub Routers

R1# show ip route


D 192.168.20.0/24 [90/2172416] via 10.0.0.2, 00:44:53, Serial0/0


D 10.0.0.8 [90/2681856] via 10.0.0.2, 00:00:50, Serial0/0

[90/2681856] via 10.0.0.6, 00:00:50, Serial0/1

D 10.0.0.12 [90/2681856] via 10.0.0.6, 00:00:50, Serial0/1



D 10.0.0.16 [90/2821632] via 10.0.0.6, 00:00:51, Serial0/1

R4# show ip route

172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks

D 172.16.0.0/16 is a summary, 00:22:16, Null0

C 172.16.1.0/24 is directly connected, FastEthernet0/0C 172.16.2.0/24 is directly connected, FastEthernet0/1


D 10.0.0.8 [90/2681856] via 10.0.0.13, 00:01:52, Serial0/0


D 10.0.0.4 [90/2681856] via 10.0.0.13, 00:01:52, Serial0/0


No 172.16.0.0 networks

Only connected networks

St b R t

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Stub Routers

R4 has a complete routingtable.


R3(config-router)# no eigrp stub connected


R4(config-router)# eigrp stub receive-only

R4# show ip route

D 192.168.10.0/24 [90/2684416] via 10.0.0.13, 00:01:19, Serial0/0

172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks



C 172.16.2.0/24 is directly connected, FastEthernet0/1D 192.168.20.0/24 [90/2684416] via 10.0.0.13, 00:01:19, Serial0/0


D 10.0.0.8 [90/2681856] via 10.0.0.13, 00:01:19, Serial0/0


D 10.0.0.0 [90/3193856] via 10.0.0.13, 00:01:20, Serial0/0

D 10.0.0.4 [90/2681856] via 10.0.0.13, 00:01:20, Serial0/0


St b Ro ters

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Stub Routers

What will R1, R2, and R3 no longer see?

R1, R2, and R3 do not have R4 LANs.

R1# show ip route


D 192.168.20.0/24 [90/2172416] via 10.0.0.2, 04:59:55, Serial0/0


D 10.0.0.8 [90/2681856] via 10.0.0.2, 04:59:55, Serial0/0

[90/2681856] via 10.0.0.6, 04:59:55, Serial0/1

D 10.0.0.12 [90/2681856] via 10.0.0.6, 04:59:55, Serial0/1



D 10.0.0.16 [90/2821632] via 10.0.0.6, 04:59:56, Serial0/1

R1#

Stub Routers

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Stub Routers


R4(config-router)# eigrp stub connected

R3# show ip route

C 192.168.30.0/24 is directly connected, FastEthernet0/0D 192.168.10.0/24 [90/2172416] via 10.0.0.5, 00:05:50, Serial0/0


D 172.16.1.0 [90/2172416] via 10.0.0.14, 00:00:52, Serial0/2

D 172.16.2.0 [90/2172416] via 10.0.0.14, 00:00:52, Serial0/2

D 192.168.20.0/24 [90/2172416] via 10.0.0.9, 00:05:50, Serial0/1




D 10.0.0.0 [90/2681856] via 10.0.0.9, 00:05:51, Serial0/1

[90/2681856] via 10.0.0.5, 00:05:51, Serial0/0



What do you expect R3 to see now?

Stub Routers X

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Stub Routers

EIGRP defines stub routers as a router which should not forward

traffic between two remote EIGRP-learned subnets.

If WAN2's LAN interface failed, and WAN1's PVC to B1 failed,

then

These conditions may well be worse than just not using this longroute.

X

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Unequal Cost Load Balancing

Variance command

Variance command

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Variance command

EIGRP does unequal cost load balancing, forwarding packets relative to the

metric. The variance command instructs the router to include routes with a metric

less than or equal to n times the minimum metric route for that destination,

where n is the number specified by the variance command.

Note: If a path isn't a feasible successor, then it isn't used in load balancing.

The maximum-pathsnumberEIGRP is used to sent the number of load-

balancing paths.

Maximum number of paths varies based on IOS version and router platform.

Was 6 routes,

Later versions supporting 16 or more.

Router(config)# router eigrp 1Router(config-router)# variance number

Variance

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command

R4#show ip route

D 192.168.10.0/24 [90/3196416] via 10.0.0.13, 00:17:10, Serial0/0

172.16.0.0/16 is variably subnetted, 3 subnets, 2 masksD 172.16.0.0/16 is a summary, 00:56:15, Null0



D 192.168.20.0/24 [90/2684416] via 10.0.0.13, 00:51:17, Serial0/0


D 10.0.0.8 [90/2681856] via 10.0.0.13, 00:51:17, Serial0/0


D 10.0.0.0 [90/3193856] via 10.0.0.13, 00:51:18, Serial0/0

D 10.0.0.4 [90/2681856] via 10.0.0.13, 00:51:18, Serial0/0


Serial0/0 is the preferred route with

a bandwidth of 1544kbps

Variance

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command

R3 via Serial 0/1 is a Feasible Successorfor all remote routes.



via 10.0.0.13 (2681856/2169856), Serial0/0via 10.0.0.17 (2821632/2169856), Serial0/1


via 10.0.0.13 (3196416/2684416), Serial0/0

via 10.0.0.17 (3336192/2684416), Serial0/1

Variance

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command

Remember, R3 is a neighbor on both links.

R4# show ip eigrp neighbors



(sec) (ms) Cnt Num

1 10.0.0.13 Se0/0 14 00:51:47 29 200 0 158

0 10.0.0.17 Se0/1 10 00:51:48 24 200 0 159

R4#

Variance

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command

Include routes with a metric less than or equal to 2 times the

minimum metric route for that destination.


R4(config-router)# variance 2

Variance

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command

Include routes with a metric less than or equal to 2 times the

minimum metric route for that destination.

FD = 3196416

Include any metric less than or equal to: 2 * 3196416 or 6392832

R4# show ip route

D 192.168.10.0/24 [90/3196416] via 10.0.0.13, 00:17:10, Serial0/0

R4# show ip route

D 192.168.10.0/24 [90/3196416] via 10.0.0.13, 00:00:37, Serial0/0[90/3336192] via 10.0.0.17, 00:00:37, Serial0/1

Before

After

Variance

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command

Via 10.0.0.17 is a Feasible Successor so it is eligible for unequal

cost load balancing.



via 10.0.0.13 (3196416/2684416), Serial0/0via 10.0.0.17 (3336192/2684416), Serial0/1

R4# show ip route

D 192.168.10.0/24 [90/3196416] via 10.0.0.13, 00:00:37, Serial0/0

[90/3336192] via 10.0.0.17, 00:00:37, Serial0/1

Feasible distance ifthis becomes a route

in the routing table

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Bandwidth allocation for EIGRP

messages

The bandwidth-percent command

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The bandwidth-percent command

Thebandwidth-percent command configures the percentage ofbandwidth that may be used by EIGRP on an interface.

By default, EIGRP is set to use only up to 50% of the bandwidth ofan interface to exchange routing information.

In order to calculate its percentage, thebandwidth-percent

command relies on the value set by thebandwidth command.

Allows EIGRP to use up to 75 percent (42 kbps) of a 56-kbps seriallink in autonomous system 209.

ip bandwidth-percent eigrp as-number percent

interface serial 0

bandwidth 56

ip bandwidth-percent eigrp 209 75

Summarizing EIGRP Routes:no auto-summary

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no auto summary

EIGRP automatically summarizes routes at the classful boundary, the

boundary where the network address ends as defined by class-based

addressing.

Summarizing EIGRP Routes:

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no auto-summary

In the presence of discontiguous subnetworks, automaticsummarization must be disabled for routing to work properly.

To turn off auto-summarization, use the following command:

Router(config-router)#no auto-summary

Summarizing EIGRP Routes: Interface

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Summarization

Router(config-if)#ip summary-address eigrpautonomous-system-numberip-address mask administrative-distance

RTC(config)#router eigrp 2446

RTC(config-router)#no auto-summary

RTC(config-router)#exit

RTC(config)#interface serial0/0

RTC(config-if)#ip summary-address eigrp 2446 2.1.0.0 255.255.0.0

Summarizing EIGRP Routes: Interface

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Summarization

RTC(config)#interface serial0/0RTC(config-if)#ip summary-address eigrp 2446 2.1.0.0 255.255.0.0

RTCs Routing Table:


Notice that the summary route is sourced from Null0, and not an actual interface. That is because this route is used for advertisement purposes and does not represent a

path that RTC can take to reach that network.

On RTC, this route has an administrative distance of 5.

RTD is oblivious to the summarization but accepts the route. It assigns the route the

administrative distance of a "normal" EIGRP route, which is 90, by default

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BAI 511

Advanced Routing Protocols

EIGRP Part 1

eigrp part 1 sep 2010

Documents